Try looking for sodium lauryl sulfate free shampoos. They are consistently more expensive than normal shampoos, but defiantly less chemical in nature. Have a look in health food shops and such, a lot tend to branch out in to toiletries and whatnot now. I know Holland and Barrett stock the Dr Organics range which are quite nice and all SLS free; http://www.hollandandbarrett.com/pag...c-products.asp

Waitrose and health food shops tend to have a reasonable range of SLS and paraben-free shampoos so you can browse for one that suits you, or you can look for 'organic' ranges online (if you want to be sure that it doesn't have too many chemicals then you need to check the ingredients list yourself though, or check that it's been certified, usually by the Soil Association). Some of them will be for women or will be unisex, but you can try baby shampoo by a more 'natural' brand to see if it works better than your current one, or a few do actually do men's ranges - I think Lavera do, for example, and Daniel Galvin Junior might do one as well.

Be careful with shampoos (or other toiletries) that claim to be free of SLS/SDS - very often they instead contain a different detergent that is practically identical anyway. SLS is the primary detergent used in a lot of shampoos, so if they remove it something else has to go in its place, and something pretty similar. Most soaps are unsuitable for use on hair and SLS does a pretty good job so it is always used, sometimes listed with a "friendly" sounding name instead.

OP - how long is your hair? If it's short you might not even need shampoo at all. If it is long then have a go using the cheapest, simplest bar soap (e.g. a supermarket's own brand of simple soap - check ingredients) and then rinse all over with a dilution of cheapo white vinegar. About 50ml in a 1L jar topped up with shower water will do fine. Rinse as little off as you can - your hair will feel amazing once it dries. The smell goes very quickly.